void main(List<String> args) {
  Persion persion = new Persion();
  persion.name = "nam";
  persion.run();
  persion.eat();
  // 级联运算符
  var p = Persion()
    ..name = "yjh"
    ..eat()
    ..run();
}

class Persion {
  String? name;

  void run() {
    print("running");
  }

  void eat() {
    print("eating");
  }
}
